Dry powder inhalers (DPIs) are an alternative to pMDI (pressurized metered dose inhaler) devices for delivering drug aerosols without using propellants. Typically, DPIs are configured to deliver a powdered drug or drug mixture that includes an excipient and/or other ingredients. Generally described, known single and multiple dose dry powder DPI devices use: (a) individual pre-measured doses in blisters containing the drug, which can be inserted into the device prior to dispensing; or (b) bulk powder reservoirs which are configured to administer successive quantities of the drug to the patient via a dispensing chamber which dispenses the proper dose.
In operation, DPI devices strive to administer a uniform aerosol dispersion amount in a desired physical form of the dry powder (such as a particulate size) into a patient's airway and direct it to a desired deposit site(s).
A number of obstacles can undesirably impact the performance of the DPI. For example, the small size of the inhalable particles in the dry powder drug mixture can subject them to forces of agglomeration and/or cohesion (certain types of dry powders are susceptible to agglomeration, which is typically caused by particles of the drug adhering together), which can result in poor flow and non-uniform dispersion. In addition, as noted above, many dry powder formulations employ larger excipient particles to promote flow properties of the drug. However, separation of the drug from the excipient, as well as the presence of agglomeration, can require additional inspiratory effort, which, again, can impact the stable dispersion of the powder within the air stream of the patient. Unstable dispersions may inhibit the drug from reaching its preferred deposit/destination site and can prematurely deposit undue amounts of the drug elsewhere.
Examples of known prior art inhalers include U.S. Pat. No. 6,536,427 to Davies et al. which proposes inhalers with blister strips that are peeled apart to expose the dry powder and U.S. Patent Application Publication No. 2007/0137645 which proposes an inhaler with a strip of blisters, each having a lid that is puncturable. U.S. Pat. No. 7,025,056 to Eason et al. proposes an inhaler for producing an inhalable aerosol of a powdered medicament that includes an aerosolizing device in the form of a vortex chamber.
Notwithstanding the above, there remains a need for alternative inhalers and/or airways for dry powders.